1. Field of the Invention
This invention relates to an image processing apparatus which converts an interlaced image into a progressive image (performs IP conversion), an image processing method, and a computer readable medium having an image processing program. More specifically, this invention relates to an image processing apparatus which, in IP conversion, reduces or removes interlace interference which occurs during slow vertical scrolling, an image processing method, and a computer readable medium having an image processing program.
2. Description of the Related Art
In the past, when displaying moving images on a liquid crystal display, plasma display or similar, interlaced images have been converted into progressive (non-interlaced) images (IP conversion).
However, when generating progressive images, there has been the problem that during slow vertical scrolling, so-called interlace interference (a sensation of flicker) occurs. For example, two blurred horizontal lines (edges) and one edge are generated periodically in a progressive image for one edge in the original image, and consequently interlace interference, with local fluctuation in the output image, occurs.
In order to reduce this interlace interference, in the prior art a video signal decoding apparatus has been disclosed in which frame or field processing judgment unit are used to judge whether, in a variable-length decoding unit, decoded data is frame-processed or field-processed in each macro block; if field-processed, an interpolation unit are used to create frame data (Japanese Patent Laid-open No. 2000-350212).
However, the apparatus disclosed in Japanese Patent Laid-open No. 2000-350212 alleviates interlace interference from an image within a single field. Hence when for example an image is slowly scrolled vertically, there is almost no advantageous result with respect to the large interlace interference which occurs at nearly-horizontal edge portions.
This is because, although horizontal lines move in the vertical direction during vertical scrolling, there are cases in which the motion vector is detected in the horizontal direction, and even when interpolation is used to generate a progressive image, because this is based on a direction which is not the scrolling direction (where interpolation in the vertical direction should be performed, interpolation is instead in the horizontal direction detected as the motion vector), interlace interference cannot be removed.